The process of creating a vapor from a liquid usually involves heating the liquid to a sufficiently high temperature to form vapor. To generate vapor at a high rate, it is necessary to supply a substantial amount of energy in a short time to the liquid so that the needed vaporization energy can be provided. Traditionally, the output of a vapor generation apparatus can be increased by increasing the operating temperature to allow more heat to flow into the liquid to form vapor. Alternatively, a larger heat transfer surface area can be provided to increase the vapor generation rate. Both approaches have been used in the past and are well known to those skilled in the art of industrial equipment design. Equipment such as industrial boilers—for generating steam from water—and refrigerant evaporator coil—for evaporating a liquid refrigerant to form vapor for cooling, refrigeration or air conditioning purposes—are examples where such approaches are used.
In semiconductor applications, a wide variety of precursor chemicals are available in liquid form to create vapor for thin film deposition on a substrate by a vapor phase process in semiconductor, integrated circuit device manufacturing. Processes such as chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVDP), metal-organic CVD (MOCVD), atmosphere pressure chemical vapor deposition (APCVD) and atomic layer deposition (ALD) are well known to those skilled in the art of semiconductor device fabrication. Some precursor chemicals such as metal-organic compounds can decompose at high temperatures to form undesirable by-products to cause process or equipment contamination. For such applications, the heating temperature must be kept low to avoid thermal decomposition and by-product formation. Increasing the heat transfer surface area will generally cause the overall physical size of the apparatus to increase, thus making the device less responsive to changing vapor demands in the process. The response speed of the apparatus will thus decrease. As a result, the traditional approach to increasing vaporization rate is not suitable for all applications.